In situ measurements of volatile organic compounds in a boreal forest 1Finnish Meteorological Institute, P.O.Box 503, 00101 Helsinki, Finland
06 Dec 2012
2Department of Physical Sciences, University of Helsinki, P.O. Box 68, 00014 University of Helsinki, Finland
Received: 02 May 2012 – Published in Atmos. Chem. Phys. Discuss.: 19 June 2012 Abstract. We present biogenic VOC, including sesquiterpenes, measurements at the SMEAR
II station (Station For Measuring Forest Ecosystem-Atmosphere Relations) in
Finland using an in situ gas chromatograph mass-spectrometer with 2 h
time resolution. The measurements were conducted over the period October
2010–October 2011, at least one week every month. To our knowledge there are
no earlier species-speciated semi-continuous BVOC data also covering dormant
periods. This was also the first time sesquiterpene mixing ratios were
measured in a boreal forest.
Revised: 05 October 2012 – Accepted: 21 October 2012 – Published: 06 December 2012
During the winter months, and still in March, the mixing ratios of all
biogenic compounds were very low, most of the time below detection limits.
The monoterpene mixing ratios increased in April and started to show diurnal
variability, with maximum mixing ratio at night and minima during the day.
The diurnal variability continued until October, after which the mixing
ratios decreased and then only occasional episodes took place. The diurnal
variation was affected by boundary layer height. Sesquiterpene mixing ratios
were very low, only a few ppt. The main sesquiterpenes were longifolene and
isolongifolene. The diurnal variation of isoprene was opposite to the mono-
and sesquiterpene diurnal curve due to isoprene's light dependent emissions.
Due to its daytime maximum mixing ratios, isoprene also dominated hydroxyl
radical reactivity in summer even though our isoprene measurements are
underestimates due to a breakthrough in a cold trap.
Citation: Hakola, H., Hellén, H., Hemmilä, M., Rinne, J., and Kulmala, M.: In situ measurements of volatile organic compounds in a boreal forest, Atmos. Chem. Phys., 12, 11665-11678, doi:10.5194/acp-12-11665-2012, 2012.